DE3689308T2 - TRAINING OF THE MOUTHPIECE OF A SUCTION ENDOSCOPE WORKING WITH ULTRASONIC AND RELATED VIBRATOR. - Google Patents

Description

SCOPE OF INVENTION

The invention relates to an apparatus for removing unwanted biological tissue. In particular, it relates to an endoscopic ultrasound aspirator with an elongated, hollow probe and simultaneous irrigation and aspiration, whereby the highly compliant tissue is disintegrated and removed from the depths of the body through a narrow surgical opening and by means of the vibrating apparatus contained in the aspirator.

DESCRIPTION OF RELATED SKILLS

The endoscopic ultrasonic aspirator (hereinafter referred to as EUA) of the present invention is particularly useful in the field of transurethral resection (TUR) of the prostate or other urological surgery, including the destruction and removal of bladder stones. More generally, it is useful in any type of surgery that requires deep penetration into the body through a narrow opening, e.g., in the case of arthroscopic surgery, discectomy, or other orthopedic surgery.

In a preferred embodiment of the invention, an ultrasonic probe with a high-velocity end-tip is insertable into the body for destruction of mobile tissue approximately 19 cm. deep while simultaneously irrigating the surgical field, aspirating fluid and tissue through a surgical opening of no more than about 29 mm in circumference, which is the maximum accepted dimension for introducing an instrument into the urethra. The circumference of the instrument may be about 29 mm, but is preferably no more than about 25 mm. A unit of measurement known as the French is often used to denote circumference. A The casing size in French units is three times the casing diameter in millimeters. Therefore, a casing with a circumference of 30 mm has a diameter of 30/π= 9.55 and a French size of 9.55·3 = 28.65.

Since the 1950s, the TUR procedure has been the preferred method for removing the diseased prostate. In a conventional procedure, the patient is placed in the conventional lithotomy position under lumbar anesthesia. An elongated resectoscope with a light source, telescope, cutting electrode and a source of continuous irrigation is inserted into the urethra and pushed up to the vicinity of the prostate, accessing the prostate through the urethral wall. The cutting electrode is a semicircular wire attached to the end of a sliding sheath for forward and backward movement; i.e., to the front and back of the patient. The electrode is equipped with a pulsed RF current that both cuts and cauterizes the tissue. The sheath is equipped with a spring in the rear direction of the patient and is repeatedly pulled forward by a trigger-like lever as the electrode planes or removes small slices of prostate tissue.

As the tissue is planed away, it is flushed into the bladder by the constant irrigation that fills the bladder approximately every 5 minutes. The collected water and shattered material must be periodically removed by a suction device such as the Ellik reamer, which has a compressible balloon connected to a flexible plastic catheter. The resectroscope is removed, the balloon compressed, and the plastic catheter inserted into the operative field. The balloon is then expanded to suction out the water and tissue debris.

This traditional method has a number of disadvantages which the present invention seeks to overcome. In order to allow the surgeon to view the surgical field, the EUA must be equipped with a viewing and illumination system. It has been determined that with the current state of optical technology, adequate endoscopic vision of the surgical procedures requires an optical relay lens system using lenses with a diameter of approximately 2.5 mm. Since these lenses must be mounted within a fixed tube which also contains illumination fibers, the overall diameter of the finished telescope is typically approximately 4 mm. In order to enable a hollow ultrasound tip to additionally remove solid prostate tissue at an adequate rate (typically between approximately 5 to approximately 10 grams per minute), the bore of the tip must also be approximately 4 mm.

In an endoscopic aspirator, both the telescope and the tip are placed side by side within a sheath. When the endoscopic aspirator is inserted into a patient's body, the sheath protects the surrounding tissue from contact with the ultrasonic tip, which vibrates not only at the surgical extremity but along its entire length.

The use of a looped electrode for cutting requires progressive cutting so that the removed tissue does not build up in front of the loop and block the viewing lens. However, as the cutting progresses, the loop is always hidden under a layer of tissue. This leads to the risk of blocking the surgeon's view and injuring the urethral sphincter, bladder wall or even the intestines can be accidentally damaged. The surgeon can also puncture the prostate capsule, the tougher outer skin of the prostate, and thus damage the blood vessels underneath. Electrical cutting is very fast, so these things can happen even with the exercise of ordinary care. Furthermore, if the EUA telescope is placed next to the ultrasound tip, the walls of the ultrasound tip will obstruct the surgeon's view of the surgical field.

The evacuation must be performed 10 to 20 times and the resectroscope must be removed each time; this can take between 20 and 50 percent of the one-hour operation time.

Another disadvantage of the current procedure is that the constant flow of irrigation, as described above, causes the filling and expansion of the bladder, and also the absorption of the fluid into the blood, leading to the risk of hypervolemia or hyponatremia. Also, electrical cutting requires the use of a relatively expensive, non-conductive fluid, such as isotonic glycine. If a conductive fluid, such as saline, is used, the cutting current may be short-circuited by the work. The fluid must be isotonic to avoid intravascular hemolysis.

Furthermore, the current procedure cannot remove bladder stones, which could require two operations when a single operation would have been appropriate.

Since the EUA is often used in the field of transurethral resection, it often has to be inserted into the urethra. Consequently, the size of the circumference of the EUA sheath is limited to the elastic expansion of the urethra, which is typically about 30 mm (or about 28 in French). However, surgeons prefer smaller sheaths, such as 24 or 25 mm (French unit) to avoid strictures or contractures of the urethra after excessive endoscopic dilation.

Removal and flushing of tissue using endoscopic ultrasound avoids these disadvantages. In the past, tissue removal by ultrasound was used for the removal of biological tissue. However, no ultrasound instrument was available for the removal of very mobile tissue through a narrow opening, such as in transurethral prostate resection. The state of the art has two major shortcomings. First, there was no long, thin probe capable of sustaining ultrasonic vibrations at high speeds at the tip, as required for the removal of such tissue. Second, the state of the art does not recognize that the most efficient tissue removal is that in which ultrasonic vibrations cause cavitation of the fluid within the cells. These vibrations should preferably be between 10 and 20 kHz, although other frequencies can be used. The term "ultrasound" is used here to refer to all frequencies of interest, including those in the audible range.

In an early development, von Ardenne and Grossman reported in 1960 the use of ultrasonic vibration to aid in the insertion of small-caliber wire probes and hollow needles into the skin. They mention the construction of a syringe adapted to inject or aspirate fluid or other material near the needle tip. They use an exponential-type velocity transducer and operate at a frequency of about 25 kHz with a tip excursion of about 10 to 100 microns.

Also in 1960, Watkins et al. reported the use of an ultrasonic chisel to break up and remove calcium deposits from heart valves. The authors explain that their skill is not applicable to soft, flexible tissue, as it was believed at the time that this tissue was relatively indestructible by ultrasonic vibration. Their apparatus operates at approximately 26.5 kHz, with a peak excursion of approximately 38 microns.

Ultrasonic energy has also been used to cavitate a fluid so that suspended microorganisms can be broken up or destroyed for either sterilization or extraction of protoplasm. This approach typically involves using a solid, round metal grain immersed in the fluid and vibrating at perhaps 20 kHz, with a frequency of about 20 to 40 microns. This works by displacing the water around the cells rather than intercellular water.

Previous patents have disclosed surgical instruments in which ultrasonically vibrating tools remove unwanted biological material while providing irrigation of the work field and aspiration of fluid and removed material. See, e.g., U.S. Patent 2,874,470 (Richards), U.S. Patent 3,526,219 (Balamuth), U.S. Patent 3,589,363 (Banko and Kelman), and U.S. Patents 4,063,557 (Wuchinich et al.) and 4,425,115 (Wuchinich). The Richards '470 device is a dental instrument that operates above the audible range, preferably at about 25 kHz, with an amplitude of about 10 microns. The device is a single half-wavelength amplifier and includes a short operating peak adapted for dental work. A magnetostrictive tube is mounted within an outer tubular casing of the device and a tight-fitting cuff is placed over the node of the tube. The part of the vibrator between the node and The vibrating tip is conveniently shown as a one-piece construction. In the Balamuth '219 device, a sharp-edged tool vibrating at about 25 kHz directly contacts the tissue to "chop" it. In the Banko and Kelman '363 device, a thin-walled, tubular tip vibrating at an amplitude of about 50 to 70 microns is used to break up and remove relatively hard biological material, such as cataract material in the lens of the human eye.

The '557 patent to Wuchinich et al. discloses a device for removing mobile tissue, e.g., neurological neoplasms, by using a magnetostrictive transducer operating at about 25 kHz with a clock rate of about 25 microns. A stepped and tapered transformer increases the clock rate to about 125 to 400 microns. However, the required gain is obtained by means of a single half-wavelength composition, achieved by mechanically joining two different materials. This distributes the required gain over a length that is insufficient in endoscopic surgery, which requires longer tips than are required in an open surgical field.

Wuchinich's '115 patent includes a first speed transfer with a second transformer connected to the front end thereof. The tool can increase the clock input generated in the magnetostrictive well by a factor of, say, five times the output at peak operation. Wuchinich's '115 patent also mentions the need to reduce voltage in a vibrating device.

The need to reduce the voltage level is also discussed in the article by E. Eisner and JS Seager entitled "A longitudinally resonant stub for vibrations of large amplitude" (Ultrasonics, Volume 3, April-June 1965, pages 88-98) which describes a tapered tool. Wuchinich's '115 patent also describes a tool having a tapered tubular portion for preferentially reducing the stress to which the metal is subjected.

None of these devices were able to achieve sufficient peak velocity and a sufficiently long and narrow probe to perform endoscopic surgery. The greatest distance that could be reached and inserted with existing surgical instruments was approximately 7 to 8 cm. More clearly, existing devices were not able to exert sufficiently firm pressure on moving cells in a biological tissue structure, e.g., a glandular tumor, to produce cavitation in the intercellular fluids of the cells or to disintegrate them in any way.

Since existing devices were not effective, it was desirable to improve the speed and efficiency of tissue removal and to produce a vibrating probe longer and faster than those previously available for endoscopic surgery.

Experiments by the inventors have shown that the effectiveness of ultrasonic vibration on biological tissues is related to the water content of the tissue. Tissue that has been allowed to drain is much less vulnerable to vibration and removal than tissue that is fresh or kept moist. It has also been found that the walls of blood vessels or muscles and brain tumors overlying contiguous tissue are much less vulnerable to ultrasonic vibration than soft, fleshy specimens such as neoplasms or muscle tissue. Since the intercellular water content of unaffected tissue is much lower than that of tissue that is more severely affected, it appears that This "tissue differential" or "tissue selective" effect appears to be related to the water content of tissues.

The present inventors realized that the tissue differential effect of ultrasonic aspiration could provide a unique advantage in endoscopic surgery, since the unwanted tissue could be removed without the risk of damaging other structures, under difficult conditions of visibility and access to the surgical field.

Because of the relationship between tissue removal and water content, the inventors hypothesized that the physical mechanism causing tissue division was the destructive effect of intercellular cavitation, that is, the formation of microscopic vapor bubbles in the intercellular fluids due to rapidly changing pressure. At a given pressure level in a fluid, the degree of cavitation is determined by a number of physical properties of the fluid, such as temperature, surface tension, viscosity, vapor pressure, and vapor density. Very important is the dependence of cavitation on (1) the applied pressure, and (2) the frequency at which the applied pressure fluctuates. Studies have suggested that the intensity of cavitation in water increases as the frequency of vibration is reduced. This hypothesis was tested by setting up two transducer tips of exactly the same size but different frequencies of pressure fluctuation. Since the pressure generated by the oscillating motion is proportional to the speed of that motion, both tips were brought to the point of tissue contact at the same speed. One tip vibrated at 40 kHz, the other vibrated at 20 kHz. In the same sample, using the 20 kHz vibration approximately doubled the rate of tissue removal, thus confirming a relationship with cavitation and disproving any assumption that tissue disruption could only be increased by increasing the vibration amplitude or speed. Similarly, it was found that the cavitation speed doubles again when the frequency is further reduced to 10 kHz. Below a threshold of 10 kHz, the speed remains constant.

There is also a pressure threshold below which it is not possible to cavitate a particular liquid. This threshold decreases in frequency down to about 10 kHz, below which the pressure threshold no longer decreases.

For these reasons, the frequency range preferably covered by this invention extends from 10 kHz to 20 kHz, and thus encompasses a portion of the ear spectrum, although lower or higher frequencies could of course be used. It was previously believed that the use of audible frequencies would be disruptive and dangerous to the surgeon and that the frequency should be restricted to the audible ranges above 18 kHz. Longer wavelengths were also discarded because a half-wavelength transducer at 20 kHz would be about 5 inches long, i.e. about the maximum length for comfortable hand-held use.

The present inventors have, however, found that other considerations must be taken into account in the endoscopic device than those previously known in the art. In endoscopic surgery, most of the vibrating components are inserted into a natural body opening, such as the urethra, so that the propagation of the audible sound is largely attenuated by the intervening body tissue. In some percutaneous applications, such as arthroscopic surgery, where only a portion of the instrument is inserted into the tissue, introduced, the propagation of noise from the external parts is minimal and can, if desired, be effectively limited by the use of dampening sleeves and covers over the transducer and part of the tip.

Even when using the most favorable frequencies, the highest possible peak velocity should be used to further increase pressure and thus cavitation. Since pressure is related to the speed of the transducer by the conventional formula P = ZV, where Z is the acoustic current resistance of the fluid, the connection between cavitation and pressure is translated into a direct dependence of cavitation on velocity.

It is assumed that cavitation is relatively independent of both the acceleration and the amplitude of the vibration.

However, the speed cannot be increased without limitation, as there is a definite physical limitation to the speed at which probes or tips made of known materials can be safely vibrated. The mechanical stress at a particular point within a vibrating tip is directly related to the tip speed at that point. Increasing the tip speed simultaneously increases the stress within the tip until it exceeds the strength of the crystal bonds within the tip material and the tip fractures. Special designs can be developed to allow high tip speeds for a given maximum stress, but the prior art designs have consistently increased the average size of the tip and have been difficult to manufacture. In addition to lowering the vibration frequency, it is therefore also an important object of the invention to reduce the cavitation rate by an improved apparatus in order to increase the possible tip speed without exceeding the maximum permissible stress for the tip material.

For a regular structure, such as a tube of constant cross-section, the tip velocity at a given point is related to the stress according to the equation s = pcv, where v is the velocity (distance per unit time), p is the density of the material from which the tip is made (mass per unit volume), c is the speed at which extensional sound waves enter the tip (distance per unit time), and s is the stress in the tip (force per unit area). In the case of titanium, which is capable of supporting the greatest stress of any commonly available material, the above relation means that the maximum permissible velocity is approximately 1270 cm per second. However, it is known that for the effective removal of living tissue, velocities of at least 2540 cm per second are preferred.

To improve tissue removal, a higher peak velocity can be achieved by using a velocity transformer that has an unequal cross-section. The above equation is only applicable to equal structures, e.g. tubes with a constant cross-sectional area. If the tube is unequal, then the equation is modified by means of a shape factor M, sometimes called a figure of merit:

s = pcv/M

Depending on how the change occurs, the form factor increases or decreases the achievable peak speed for a given maximum voltage. Of interest in this case is achieving a peak design whose form factor is greater than one.

From the modified equation it is clear that for a certain maximum permissible voltage the peak speed can be increased beyond that which can be achieved in a similar tube by a factor M.

There are a variety of tip designs in which the cross-sectional area varies along the length to achieve an M value that is substantially greater than one. For example, exponential tips whose cross-sectional area varies along the length can be designed as

Area = Aoe-aL

where e is the natural base, Ao and a are constants, and L is the distance from the point in question to the end of the tip, theoretically form a shape factor equal to e or 2.7. However, to achieve this, the M value requires that the tip begin and end with drastically different diameters. A tissue-removing device of an exponential design with a shape factor of 2 that could comfortably produce a tip velocity of 25.4 m/sec would begin with a diameter about five times that of the surgical end. In an endoscopic device that must penetrate a few centimeters into a narrow body orifice, an exponential design is not practical. If designed to accommodate the limits of the human anatomy, its tip would be too small to remove tissue at a practical speed.

It was found that the most efficient design for increasing the M value from 1 to about 2 was to use a constant load speed transformer coupled with a speed transformer of constant diameter. In a uniform tube, which produces extensional vibration, the load follows the relation

s = sin πx/L,

where x is the distance to the point in question from one end of the tube, and L is the total length of the tube. From this relation it can be seen that the load is greatest at x = L/2. Consequently it would be desirable to provide at the working end of the surgical probe with length L/2 another part with a different cross-sectional area so that for values of x greater than L/2 the load remains constant at the largest permissible value.

Also, such a design would provide the greatest possible extension for a given maximum stress. Since Hooke's law dictates that the extension of any part of the transformer is subject to stress, and since the stress is constant, the extension increases linearly along the tip length beyond its midpoint.

It is shown below that such a tip, in the area designed for constant stress, has a cross-sectional area that satisfies the relation

Area = Be-by2

where B and b are constants, and y is the distance from a given point to the end of the tip. This mathematical function is known as the Gaussian function, after the mathematician Gauss who studied these values. Consequently, the tip with constant stress is called a Gaussian resonator. Gaussian resonators represent a significant improvement over any alternative design because they can be manufactured with diameters that can be accommodated by the human anatomy with a sufficiently large tissue contact area and aspiration passageway to permit effective tissue removal, and a form factor of 2, thereby enabling a velocity of 25.4 meters per second to be practically achieved in an endoscopic or percutaneous device. Furthermore, the Gaussian design does not require a large difference between the two final diameters.

The cross-sectional area decreases progressively along the length of the resonator so that the stress remains constant; however, this need not occur near the tip end that contacts the tissue. Since there is no stress at this point, the stress is zero, so the end of the tip need not be designed to withstand the same stress, but can be shaped and rounded so that the stress is gradually reduced to zero.

The mathematical basis for creating a Gaussian resonator in the EUA is as follows: Well-established acoustic principles create the parameters that result in the highest speed emanating from thin poles undergoing simple extensional vibration. For a uniform pole with both ends free, the highest achievable speed is directly related to the highest stress that the material from which the pole is made can safely withstand:

Vmax = Smax/pc (1)

where Vmax is the speed (distance per unit time), Smax is the safe stress limit (strength per unit area), p is the material density (mass per unit volume) and c represents the speed at which extensional waves travel in the material (distance per unit time). Since metals are the only practical materials capable of sustaining the high-level acoustic vibration we are interested in, and since c represents approximately the same thing for all these metals, namely, obtaining the largest possible Vmax value, a material should be chosen which has the highest possible force-to-weight ratio (Smax/p). The well-established material is aircraft titanium. The safe value of vibration stress has been found experimentally to be one-third the value of the yield stress (the stress at which the metal begins to deform irreversibly). If Vmax is calculated using the appropriate values of Smax, p and c, it turns out that

Vmax = 1219 cm/sec. (2)

with a uniform pole made of aircraft titanium.

However, this speed achieves only a small degree of soft tissue removal, even if the vibration frequency is reduced to increase cavitation of intracellular water. A value approximately twice that of equation 2 is desirable for effective disintegration of this tissue. Consequently, a velocity transformer is required which approximately doubles the value of Vmax without increasing the maximum load above Smax. It is also desirable in an endoscopic device that this velocity transformer be implemented within a narrow circular channel, preferably approximately 8 mm in diameter, of which approximately 4 mm consists of a circular aspiration bore. It is therefore important that the velocity be increased with a minimum change in cross-sectional area so that the entire resonator within the endoscope is exposed to a Length of at least approx. 17 to 19 cm can be placed.

Fig. 1 shows a hypothetical velocity transformer consisting of a unitary section of a quarter wavelength followed by an integral second section of length L. Fig. 2 shows various possible stress distributions in this pole, for various hypothetical cross-sectional variations of the second section bar. The velocity at any point to the right of the unitary section can be represented as

v(x) = [=2πf/E] Sxo s(x)dx (3)

where s(x = o) = Smax, s(x = L) = o, f is the frequency of the vibration (period per unit time), and E is the elastic constant or Young's modulus (strength per unit area). Consequently, the velocity distribution along the section can be calculated directly from these stress distributions. At any point, the velocity is related to the area within the stress curves at that point. In Fig. 3, these respective velocity distributions are shown. Although it produces the highest final velocity, curve 1 exceeds Smax and would therefore not be a practical choice. Curves 2 and 3 produce safe stress distributions, but do not give the highest achievable final velocity. The areas under these curves in Fig. 2 are less than the areas under curves 1 and 4.

Only curve 4 increases speed the fastest, while maintaining a safe working load. Curve 4 represents a constant load plane in the section, except at the terminus, which is exposed and therefore not subject to pressure.

It remains to determine how the second section must be shaped to achieve this optimal load distribution. The velocity distribution in an extensional, vibrating, thin pole is related to the velocity and cross-sectional area as

Since s(x) = Smax, for O ≤ x ≤ L, (5)

and since δs(x)/δx = O (6)

then v(x) and s(x) are related by equation 3 with s (x) = Smax, which gives v(x) = -2πf/E·Smaxx (7) .

If equations 5, 6 and 7 are replaced by equation 4, the state

which, when integrated between A(x=o) = Ao and A(x), and between x=o and x=x, yields A(x) = Aoe(-k2x2/2), O ≤ x ≤ L,

where k² = [2πf/c]². (9)

Consequently, to achieve the optimal velocity transformation, the cross-sectional area of the resonator must be progressively decreased from its value at x = o, as prescribed by equation 9, which represents the Gaussian function.

There is no theoretical limit to the extent to which the velocity increases as long as A(x) satisfies equation 9. In practical terms, the resonator is hollow, and the wall thickness required for the ever decreasing values of A would eventually produce a structure that would not be sufficiently strong for handling in medical treatment. However, the Gaussian resonator exhibits a velocity transformer factor of at least 2, with an acceptable initial cross-sectional area Ao, making the achievement of tissue disruption with an endoscopic device practical.

Amplification of the constant stress can also be achieved in a uniform structure, e.g. a cylindrical tube, by changing the elastic constant E, or both the elastic constant E and the density p, along the length of the structure, without changing the cross-sectional area.

An example is a system in which density is proportional to the elastic constant, i.e. p = nE, where n is a constant. It is found that constant stress in such a system can be achieved if E is varied according to the Gaussian function:

E + Eoe-n(2πfx)2/2, (10)

where E(x=o) = Eo. Consequently, the elastic constant E decreases from the vibration input to the free end of the resonator. Under these circumstances,

v(x) = 2πfSmax Sxo [s(x)/E(x)] dx. (11)

Since S(x) = Smax in a system of constant stress, v(x) = -2πf Smax Sxo 1/E(x) dx. (12)

Since E(x) is a decreasing function, the integral in equation (12) increases faster than it would if E(x) were a constant function, as in of equation (3) above; therefore, a larger velocity amplification can be expected under these circumstances than in a system in which the cross-sectional area is varied to achieve constant stress conditions.

According to the invention, a vibration apparatus for an endoscopic ultrasonic aspirator comprises a vibration source for vibrating at a high frequency and at a first amplitude; a first speed transformer having an input end and an output end, the input end being coupled to the vibration source for vibration thereby, the output end vibrating in response to the vibrations received at a second amplitude greater than the first amplitude; a second elongate speed transformer having an input end and an output end, the said output end corresponding to the operating end of the apparatus; the input end of the second speed transformer being connected to the front end of the first transformer for vibration thereby, the output end vibrating in response to the vibrations thus obtained at a third amplitude which is greater than said second amplitude, the second transformer being of unitary construction and having, during the vibration process, a substantially constant mechanical stress level along substantially its entire length. The second transformer may have a cross-sectional area which varies from its input end to its output end so as to produce said substantially constant mechanical stress level. The cross-sectional area of the second transformer may vary according to the Gaussian function. On the other hand, the substantially constant stress level may be produced without changing the cross-sectional area by varying the elastic constant of the material of the transformer. or both the elastic constant and the density of the material can be changed.

The invention also provides an endoscopic ultrasonic aspirator comprising the aforesaid vibration source maintained within a hollow handpiece for generating mechanical vibrations in response to alternating current supplied to the vibration source; an elongate sleeve having a hollow bore communicating with the interior of the hollow handpiece and having an operating end remote from the handpiece; means for supplying said alternating current to said vibration source; elongate tool means connected to the vibration source and extending through the hollow bore of the sleeve to a working area behind the operating end of the sleeve for delivering said mechanical vibrations to said working location; viewing means extending from the handpiece to said working area for obtaining a view of the handpiece of said working area; a means for supplying fluid into a fluid space defined between said tool means and said hollow bore of said shell; and a fluid indicating means for detecting the presence of fluid in the fluid space and connected to the means for supplying alternating current for stopping the supplied alternating current and thereby terminating the mechanical vibration when fluid is not present.

In another form of the invention, an apparatus for removing unwanted biological material comprises a handpiece; an elongated sheath extending from the handpiece and having a hollow bore; and containing the vibration apparatus of claims 1, 2, 3, 4, 5 or 6 as described in claim 15.

In another aspect, the suction means also includes a biopsy valve coupled to the fluid passageway to which suction is applied for selectively distributing fluid and tissue therefrom, and also a capture means for capturing and filtering the desired fluid and tissue which have been selectively captured.

The application of the invention in transurethral resection of the prostate provides several benefits, including: 1) tissue differential action, 2) thermal cauterization and absence of necrosis, which should greatly accelerate healing, 3) the backward movement of the instrument, which allows direct visualization of the procedure, 4) the ability to remove bladder stones or the like, and 5) the reduction in time (and hence increased safety) of the procedure by increasing the speed of tissue removal and by allowing for a continuous operation.

The tissue-reading capability of the endoscopic ultrasound procedure reduces the risk of puncturing the prostate capsule or bladder unless the instrument is forced by the surgeon. Any obstructions, such as blood vessels, are easily felt by the surgeon since the handpiece is mechanically connected directly to the operating tip, which inevitably leads to a safe procedure that can be used with less training than was the case with the previous procedure.

Consequently, the ultrasound procedure also causes minimal microscopic tissue deformities, allowing more accurate histological diagnoses. The aspirated tissue can be quickly directed into a biopsy trap of the system and removed for analysis. Another advantage is the elimination of electrical current through the patient's body, which the risk of shock, burns or obturator nerve reflexes is avoided.

The constant suction of debris and water reduces the operating time to just half an hour. This results in a reduction in surgical bleeding and a general reduction in the surgical risk for patients. The further reduction in bleeding is due to the caustic effect of the friction of the moving tip on the adjacent tissue.

Also, removing the tissue using ultrasound, along with constant irrigation and suction, allows for retrograde incisions, giving the surgeon a better view of what is in the way of the incision edge. Because the pieces of tissue removed are small, they are easily suctioned away, allowing the surgeon to make a continuous incision with good visibility for any length of prostate tissue to be removed.

An embodiment of the present invention also relates to an endoscopic ultrasonic aspirator with a tip of reduced circumference, which provides the surgeon using the aspirator with an expanded view of the surgical field.

Another embodiment of the invention relates to an improvement in an endoscopic ultrasonic aspirator of the type including a resonator having a vibrating tip for removing biological material, means for supplying fluid to the tip, means for removing the fluid and ablated biological material, and means for viewing the operation of the vibrating tip. This improvement includes open channel means connected to the resonator tip for enabling viewing of the tip while it is in use, and means for supporting the open channel means and forming a passage to assist in the correct operation of the aspirator in removing the fluid and ablated biological material. If desired, the entire length of the resonator may be shaped and dimensioned in the form of the open channel means so that the viewing means may be partially received, held and supported by the open channel means, thus minimizing the size of the aspirator. Preferably, the means for supporting the open channel is a resilient plug and the channel means has a U- or V-shaped cross-section.

According to a preferred embodiment of the present invention, the tubular ultrasonic tip of the aspirator is cut lengthwise. The telescope is then suspended within the cut-out tip portion. Consequently, the end of the ultrasonic tip has a U-shape in cross-section, with the suspended telescope within the U. As a result, the opening of the U-shaped tip is partially closed by the lower surface of the telescope, so that a cross-section of the opening at the tip, near the operative end, has a crescent shape.

Because the telescope is inserted into the end of the ultrasonic tip, the overall circumference of the aspirator end of the present invention is smaller than that of an aspirator end in which the ultrasonic tip is circular in cross-section where the telescope is attached adjacent to the ultrasonic tip. Because the upper part of the ultrasonic tip adjacent to the telescope has been removed, the surgeon's view of the surgical field is not blocked by the ultrasonic tip. To ensure that the respective positions of the telescope and the ultrasonic tip do not change, a plug can be inserted between the telescope and the U-shaped tip. The ultrasound tip and plug are then mounted within a shell or lower cavity that is connected to the upper cavity in which the telescope is mounted.

Other objects, features and advantages of the invention will become apparent from the following detailed description of the preferred embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows a hypothetical extensional resonator to explain the background of the invention.

Fig. 2 shows a group of curves to show possible voltage distributions in the resonator of Fig. 1.

Fig. 3 shows a group of curves to show velocity distributions, corresponding to the curves of the stress distributions of Fig. 2.

Figures 4A and 4B together form a partially broken away view of an endoscopic ultrasonic aspirator (EUA) according to an embodiment of the invention.

Figure 5A is an elevational view of a resonator assembly including a converter and first and second velocity transformers for use in the EUA of Figures 4A and 4B.

Figure 5B is a graphical representation of the extension and stress distributions in the components of Figure 5A.

Figure 5C shows an alternative resonator composition.

Fig. 5D shows another alternative resonator composition.

Figure 6 is an end view of the EUA, taken along line 6-6 of Figure 4B.

Fig. 7 is a detail of Fig. 6 showing an end view of the telescope 28 of the EUA.

Figure 8 is a plan view of a sealing ring 112 used in the EUA.

Figure 9 is an elevated view of a portion of an alternative embodiment of the invention.

Figures 10A and 10B together form a block diagram of an ultrasonic power supply for use with the EUA.

Figure 11 is a cross-sectional view of the EUA taken along line 11-11 of Figure 4A.

Figure 12A shows a schematic of an irrigation system for use with the EUA.

Figure 12B shows a schematic of an extraction system for use with the EUA.

Figure 13 is a schematic diagram of part of an alternative ultrasonic power supply for use with the EUA.

Figure 14 is a perspective drawing of an open channel embodiment of the endoscopic ultrasonic aspirator of the present invention.

Figure 15 is a cross-sectional view of the embodiment of Figure 14, taken along line 15-15.

Figure 16 is a cross-sectional view of the embodiment of Figure 15, taken along line 16-16.

Figure 17 is a cross-sectional view of the embodiment of Figure 15, taken along line 17-17.

Fig. 18 is a cross-sectional view of the embodiment

Fig. 15, along line 18-18.

Figure 19 is a view of the transformer input section of the invention.

Fig. 20 is a view taken along line 20-20 of Fig. 19.

Figure 21 is a view of the transformer input of the invention when the telescope is inserted.

Fig. 22 is an illustration of the transformer input section with the telescope inserted and further sealed with an elastic material.

Fig. 23 is a view of Fig. 22 with a portion of the elastic sealing material removed.

Figure 24 is a cross-sectional view similar to Figure 15, but showing an alternative embodiment of the invention.

Figures 25, 26 and 27 are detailed views of resonator tip modifications for the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In Figures 4A and 4B, an endoscopic ultrasonic aspirator according to a preferred embodiment of the invention is shown. A handpiece 20 is attached to what is referred to as the rear end of the device. A sheath 22 extends from the handpiece 20 toward what is referred to as the operative end of the device. A support assembly 24, integral with the sheath 22, couples the handpiece to the sheath. The handpiece is preferably made of plastic, and the support assembly and sheath are preferably made of metal. The EUA also consists of a straight telescope 28 which extends horizontally from the rear end to the operative end of the EUA. A horizontal, Upper wing 26 of the handpiece 20 includes an opening 30 through which the telescope passes to the exterior of the handpiece. The handpiece also includes a lower wing 32 which together with the upper wing 26 forms an angle A. The angle A is best suited to be about 20 to 45 degrees, since its purpose is to allow various components to be located within the handpiece without interfering with the straight, horizontal line of sight required by the telescope.

The sheath 22 is connected to the handpiece 20 by means of a retaining assembly 24 which is integral with the sheath 22 at the rear end thereof. The retaining assembly 24 is generally cylindrical and has a circular opening at its rear with inwardly directed threads 34. The handpiece is circular at its front end and has outwardly directed threads 36 adapted for screwing the lock 24 into the threads 34. The lock 24 has a front portion 38 with annular surfaces 40 and 42 facing rearward and forward, respectively. The handpiece is screwed into the rear opening 30 of the retaining assembly until it contacts the rear surface 40. The front surface 42 of the lock 24 limits the distance at which the operating end of the sheath 22 of the EUA can be inserted into a surgical opening.

The telescope 28 has a magnifying glass 50 at the rear end and a cable 52 for supplying electrical power to an electro-optical light source 54. The telescope extends from the magnifying glass in a straight line of sight to the operational end of the EUA. The design of the telescope is shown in more detail in Fig. 7. The telescope includes a cylindrical lens system 56 located near the lower part of the cylindrical inner surface 58 of the cylindrical telescope 28. In the crescent-shaped space between the inner surface 58 and the lens system optical fibers 60 are arranged which transmit light from the light source 54 to the operating end of the telescope. Other treatment sources can be created. In this embodiment, the outer diameter of the telescope 28 is about 3 to 4 mm, and the outer diameter of the lens system 56 is perhaps 1.7 to 2.7 mm, depending on the size of the entire telescope 28.

Mounted within the handpiece and sheath is a general resonator assembly 68. The resonator assembly 68, which is more clearly visible in Figure 5, includes a piezoelectric transducer 70; a first velocity transformer 72 having a relatively thick arcuate input portion 74 coupled to the transducer for receiving vibration energy therefrom, and an integrally narrower output portion 76 projecting forwardly from the input portion 74; and, integrally connected to the front end of the output portion 76, a velocity transformer 78 extending from the output portion 76 to the operating end of the EUA and projecting slightly beyond the sheath 22. The length of the transducer is substantially one-half of one of the wavelengths of the vibrations used in the device. Consequently, the converter has anti-node vibrations at its ends and a node halfway between its ends. The length of the arcuate input portion 74 of the first transformer 72 is one-quarter wavelength; consequently, its point of contact with the converter 70 is an anti-node vibration and its point of contact with the output portion 76 is a node. The length of the output portion 76 is one-half wavelength. Therefore, there is an anti-node vibration at the center of this portion and a node exists where it is connected to the second speed transformer 78.

The second transformer 78 is of the Gaussian type described above. As can be seen in the schematic in Fig. 5, there is little longitudinal extension and little stress in the input section 74 because it is relatively massive and a significant portion of its vibration consists of bending vibration. The stress is high at both ends of the output section of the first transformer, but is zero at the central point which consists of a vibrating belly or loop with the greatest longitudinal extension. The stress in the output section 76 is at the highest permissible level for the material and design used, in other words, Smax, as defined above. The Gaussian resonator 78 exhibits constant stress at this same level Smax, throughout almost its entire length, almost to the tip 80 at its operating end. The stress near the tip 80 is essentially zero since normally there is little or no stress on the tip.

As can be seen in Fig. 6, the second transformer 78 and the output section 76 are not round. Rather, these sections are free of curvature at the top and bottom to allow for ample water flow without substantially changing their vibration characteristics. The central bore 110, however, is essentially circular, with an inside diameter of perhaps 4.33 mm (13 in French).

The operating end 80 need not be in a vertical plane as shown, but may be angled or otherwise shaped if desired in a particular application.

The combined length of the output section 76 and the second transformer 78 is conveniently about 19 cm. If desired, it could be extended many times by half a wavelength; that would be about 13 cm at about 20 kHz.

A piezoelectric transducer as used here typically has a maximum vibration amplitude of about 23 microns. At the frequencies of interest here, an amplitude of about 350 microns is required for peak vibrations at the required speed. Resonator composition 68 provides this 15-fold increase in vibration amplitude.

A groove 90 is formed in the top of the transformer input section 74 and is sized to receive the telescope. The groove 90 allows the telescope to be placed almost parallel with the transformer sections 76 and 78 within the forward end of the enclosure to form a compact and tight enclosure without interfering with the receiving section 74.

The letter R in Fig. 5A refers to the radius of curvature of the arcuate receiving section 74. This radius must be small enough to allow the handpiece to curve far enough below the line of sight of the telescope - at least about 20 degrees would be desirable - to provide a compact and easy-to-handle unit. A radius R of about 5 cm gives an angle of about 40º. At an operating frequency of 20 kHz, 5 cm is about 0.2 times the wavelength. Preferably, the radius R should not be less than about 0.1 times the operating wavelength to avoid excessive energy losses. Thus, the radius should be less than about 0.5 times the wavelength to provide a useful offset angle of about 20º along the length of the input section 74, which is about 6 cm. The arc shape of the input part is not necessarily circular; therefore the radius R is defined here as an approximate value.

Figures 5C and 5D show alternative resonator compositions 68c and 68d. In Figure 5C, a first transformer 72 is coupled to a converter 70. As in the previous embodiment, the first transformer is a half-wave tap transformer. Coupled to the operating end of the first transformer is a second transformer 78c having a constant cross-sectional area. Speed Gain is achieved by increasing the elastic constant of the material in the second transformer from its point of contact with the first transformer to its tip 80c. Optionally, the material density of the first transformer may be reduced as a function of the distance from the first transformer to the tip.

In the embodiment of Figure 5D, the same second transformer 78c as just described is used. In this embodiment, however, the first transformer 72d, which is bent as in the previous embodiments, is not a tapped transformer. Rather, the speed gain in the first transformer is achieved by increasing the elasticity of the material of the first transformer and optionally decreasing the density of the material as a function of distance from the transformer. As can be seen in Figure 5D, the transformer 70 and the first transformer do not necessarily have to have the same cross-sectional area at their coupling to achieve sufficient energy transfer.

Due to the curvature of the part 74, the transformer parts 74, 76, 78 may undergo a certain small number of transverse bending variations. However, all of the transverse vibration components in the parts 76 and 78 are damped by the presence of irrigation fluid in the surrounding space 98 within the envelope.

Irrigation fluid is supplied through a hose 92 and is controlled by a valve 94. The irrigation fluid flows through a radial bore 96 in the outer part of the front section 38 of the support assembly 24. It then flows into the spaces 98 surrounding the resonators 76 and 78 within the shell. As generally indicated in Fig. 6, the groove has a generally ovoid cross-section. Its circumference should preferably be about 25 mm, approximately the same as the circumference of a circular instrument with a diameter of 8 mm, which dimension is known in the art as 24 French units. If necessary, a circumference of about 29 mm, corresponding to 28 French units, is usable. With 28 French units, or larger instruments, there is a risk of injuring a narrow opening, such as that of the urethra. The telescope 28 is located in the narrower part of the ovoid sheath 22. It is enclosed by epoxy material or the like which extends inside the sheath to form a compartment 100 which forms a watertight compartment for the telescope.

Irrigation fluid flows toward the operating end of the EUA through space 98 from around barrier 24, and dampens any transverse vibrations of transformer portions 76 and 78, as well as irrigating an operating field near tip 80. Temporary fluid passages may also be created. Fluid is prevented from flowing into the handpiece by a sealing ring 112, as shown in Figure 8. The ring is generally O-shaped, but has a smaller opening in its upper portion to accommodate the telescope. Sealing ring 112 seals the annular space around input transformer portion 74 within the handpiece, and forms hole 114 for the watertight passage for the telescope.

Additional sealing and support is provided by an O-ring 120 that extends around the transducer within the wall of the lower handpiece wing 32. The O-ring 120 is located at the vibration node in the center of the transducer.

The coupling between the converter and the input part 74 can advantageously contain hollow threads which are countersunk into the abutting surfaces of the suction passages 110 of the converter and the input part, and also a hollow threaded pin which is inserted into this both. Such a connection enables a smooth, fine machining of the adjacent surfaces of these two resonator elements and results in a good acoustic coupling between the surfaces.

Referring again to Figures 4A and 4B, suction is provided through a continuous concentric bore 110 extending from the tip 80, through the second transformer 78, the first transformer 72 and the transducer 70, to a tube 122 connected to a suction source. Other passageways may additionally be created. Through these means, fluid and removed tissue flow away from the surgical field and are aspirated by the EUA away from the surgical field for either disposal or histological analysis.

The edges of the operating end of the second transformer 78 are rounded at the tip 80 to allow removal of tissue to occur by cavitation of intracellular water, as previously discussed, without indiscriminate cutting by the tip 80 which could inadvertently cause injury to tissue that was not intended to be ablated.

It is important for all transverse vibration components of the transformer parts 76 and 78 to be dampened by liquid flowing into the spaces 98, and for the vibration to cease if no liquid is present. For this purpose a liquid sensor is provided in the form of an insulated wire 124 running rearwardly along the telescope and separated from the liquid space 98 by the partition 100. The wire 124 passes through the hole 114 in the sealing ring 112, and through the groove 90 in the input part 74 to the interior of the handpiece. The wire could also be sunk into a groove, ie either in the partition 100, in the bore surrounding the telescope, or in the bore enclosing the resonators, should This may be desired. It may also be exposed to liquid if adequate insulation is provided. The wire is so fine that it does not interfere with the seal provided in the sealing ring 112. The wire 124 is then passed around the O-ring 120 to the exterior of the handpiece. As explained below, means are provided in the high frequency power supply circuit for detecting the load between this wire 124 and the second transformer 78 which is grounded. Should the load increase, indicating the absence of water, vibration of the transducer 70 is stopped to avoid excessive transverse vibration and possible damage to the resonator components.

Figure 9 shows elements of an alternative embodiment of the invention. In this embodiment there is no partition between the telescope 28a and the irrigation fluid containing space surrounding the resonators 76a, 78a. To support the telescope, a quantity of 82 biologically neutral silicone rubber adhesive or the like is placed between the telescope and the junction of the resonators 76a and 78a. It is important to use a flexible adhesive to allow relative movement even though this junction represents a vibration node, since each point on each resonator undergoes a small degree of radial vibration, which is natural for a body subjected to extensional vibration. Since any additional part of a resonator is compressed, it readily buckles immediately. Consequently, each point on each velocity transformer is constantly undergoing a slight radial expansion and contraction. These radial vibrations should be isolated from the telescope. However, there can be no more than about 250 to 500 microns of separation between the telescope and the resonators due to the severe limitation on the size of the envelope. This requirement In view of the further requirement for vibration isolation, the need for proximity is solved by connecting the elements with an adhesive.

The ultrasonic generator and related circuitry for powering and controlling the ultrasonic transducer 70 are shown in Figs. 10A and 10B.

The transducer 70 includes an elongated toroidal piezoelectric crystal 71 driven by a cylindrical high voltage electrode 84 and an annular ground electrode 86. (See also Figs. 4A and 11). The ground electrode 86 is electrically connected to a conductive liner 116. The liner 116 runs the length of the transducer 70, feeding the exhaust duct 110 and electrically coupling to the speed transformers. The transducer is insulated with cylindrical insulators 88a, 88b, 88c located at the ends of the transducer and between the electrodes 84 and 86.

The piezoelectric transducer and tip are driven by the generator via a bipolar coaxial cable 130. It receives power from an AC signal whose magnitude and frequency are controlled by a DC-AC converter 132. This converter converts an input DC voltage into an AC signal having a frequency controlled by an AC signal supplied to the frequency control input 134 and a magnitude controlled by a DC voltage level supplied to the converter at its magnitude control input 136. The frequency provided at the input 134 is the frequency at which the transducer is driven to vibrate. The DC voltage supplied to the input 136 is that required to maintain a selected vibration amplitude at the vibration frequency.

The frequency and voltage stimuli are received by a feedback signal by applying two signals proportional to the voltage and current input to the converter. In Fig. 10, C₁ and C₂ form a capacitive voltage distributor which produces a voltage across C₂ which is directly proportional to and in phase with the converter voltage. The voltage across C₃ is proportional to the converter current, but is out of phase and 90 degrees. The voltage between the contact arm of the potentiometer R₁ and ground is the feedback signal. When R₁ is set correctly, the feedback signal is very low at all stimulus frequencies except the resonant frequency of the converter, because at resonance the converter voltage and current are 90 degrees out of phase.

At resonance, when the feedback signal is present, its magnitude is proportional to the vibration amplitude, and its phase exactly equals that of the transducer output signal.

The inductance L reactively cancels the static load capacity of the transducer; i.e., the load capacity of the cable 130 and the net load capacity of the voltage distributors C₁, C₂. This load capacity is conveniently neutralized so that the voltage on the contact arm of R₁ will be in proportion to the vibration amplitude, and at frequencies other than resonance it will be very low.

The feedback signal is passed to two control loops: one to achieve the correct frequency and the other to achieve the desired vibration amplitude. If the aspirator is demagnetized, there is of course no feedback signal and a means of generating the vibration must be provided. A predetermined start signal is provided by a voltage controlled oscillator 140. In the absence of any feedback, this oscillator runs at a frequency which is set by a variable Resistor R3 is matched to the general range of expected transducer resonance. Generally, since this initial stimulus frequency is not the resonant frequency, a significant feedback signal will not occur. However, acoustic resonators exhibit a fairly reduced vibration level at frequencies within about five percent of their true resonance. Consequently, a small but detectable feedback signal is generated.

In the frequency control loop, the feedback signal enters a very sensitive phase comparator 142 which produces a DC voltage proportional to the difference between the phase of the feedback signal and the phase of the output of the voltage controlled oscillator. The frequency of the feedback signal is the same as that of the oscillator, but the phase is not the same because the frequency has not yet reached the resonant frequency of the converter. The output from the phase comparator is greatly amplified by a phase error amplifier 144, and then passes through a limiter 146 which limits the output of the amplifier up and down. This amplified signal, subject to the limits of the limiter, is then provided to a steering input 148 of the voltage controlled oscillator 140 and modifies its output frequency until the phase difference between the feedback signal and the voltage controlled oscillator output signal is reduced. The voltage controlled oscillator frequency that produces this result is the true resonant frequency of the converter.

The result of limiting the control voltage range applied to the oscillator at input 148 is to limit the extent to which the frequency can be shifted. In general, a complex acoustic resonator, e.g. the transducer 70, has more than one extensional resonance, with only one capable of providing the desired performance. Stimulation of other resonance frequencies would result in much lower vibration levels and very poor tissue dissection. Since the vibration levels at these parasitic resonances are much lower and produce less total vibration energy, if precautions are not taken, the system would naturally tend to operate at frequencies where the workload is less. The limiter 146 prevents the oscillator from being driven to frequencies outside a predetermined bandwidth which narrows the intended resonances.

In the amplitude control loop, the feedback signal is fed to an equalizer 150 which produces a DC voltage proportional to the magnitude of the feedback signal. A choke filter 152 eliminates all AC components and filters out only the direct current component. This signal is then subtracted from a preselected DC voltage by means of an over-threshold 154. The difference between these two voltages is greatly amplified by an amplitude error amplifier 156, and is fed to the main power supply 160 to control its DC power voltage. This DC power voltage is the power source for the converter 132. It is proportional to the magnitude of the converter's AC power signal, which in turn is proportional to the vibration amplitude of the converter 70. This amplitude control loop maintains the amplitude of vibration desired by the operator regardless of the current drawn by the transducer 132 through the converter 70, providing consistent performance in the presence of both compliant and resistant tissue.

Since the current available from the converter is not unlimited, an internal circuit is created in this component to safely limit the maximum current consumption from the converter, thereby eliminating unsafe current demands caused by voluntary or involuntary misuse. When the converter's current limit is reached, the vibration amplitude output is automatically reduced. The amplitude is restored at the control knob once the excessive current demand has been eliminated.

Also shown in Fig. 10A is a capacitance sensor 162 which measures the capacitance between capacitance finder 124 and ground. If this capacitance increases significantly, indicating the absence of water around the speed transformers 72 and 78, the capacitance sensor 162 will bring the input level to an input 138 of the converter 132 to a level which will inhibit the converter and terminate the AC power from the converter.

Figure 12 shows an entire endoscopic ultrasound aspiration system. An irrigation fluid source 170 is placed approximately 1 to 2 meters above the EUA. This distance provides sufficient hydrostatic pressure so that the phase neither expands nor collapses.

Aspirated fluid and tissue pass through the suction tube 122 to a biopsy valve having two positions 172. Normally, the debris is directed from the valve 172 through a direct tube 174 to the suction source. However, if the surgeon sees suspicious tissue from which a biopsy is desired, the valve 172 can be switched to direct the debris into a biopsy trap 176. The biopsy trap is a watertight container with a transverse sieve 178 through which the aspirated debris must pass. The desired tissue can be rapidly collected on the tray and taken for histological analysis. The biopsy trap should be relatively close to the EUA, e.g., approximately 0.3 to 0.5 meters. Because of the proximity, the tube 122 can be cleared very quickly so that the biopsy material can be collected without undue delay after the suspicious tissue has been viewed. The trap can also be kept sterile so that samples can be collected without contaminating the sample itself or the surgeon's gloves.

The aspirated debris then passes through a line 179 to the main aspiration trap 180. The trap 180 is a closed container with an entrance 182 surrounded by a stocking-shaped screen 184 through which the debris is filtered. After screening, the tissue can be removed in its entirety for medical examination. The trap is equipped with an exit 186 from the screen 184.

The sieves 178 and 184 are not particularly fine. Their openings can conveniently be about 1 mm square, so that blood clots, etc., can pass through without clogging. On the other hand, the sieve density is selected to catch pieces of tissue the size of which is approximately the same as the inner diameter of the operating tip 80, which has approximately the dimension of the tissue which is peeled from the organ to be removed.

After screening, the debris passes through a line 188 to a vent valve 190. The valve 190 has a check valve 192 which opens and passes the pressure on the line 188 to a vacuum switch 194 when the pressure on the line 188 falls to a predetermined low level, which would indicate that the system is clogged. If the vacuum switch 194 opens, a solenoid 196 also opens, thereby opening a vent line 198, thereby venting the suction pressure to the atmosphere.

The overall control of the suction pressure is carried out by a main valve 200, operated by a solenoid 202.

Pumping is done by a peristaltic pump 210.

The aspiration fluid to be excreted is collected in a collection container 220.

Figure 13 shows elements of an alternative generator for driving the EUA in electrical tissue cauterization. A two-position double pole switch 230 is used to select the signal source applied to the transducer cable 130. In one position, the switch selects the transducer drive signal across the capacitors C1, C2 in the generator system as previously explained with respect to Figures 10A and 10B. In the other position, the conductor and coaxial shield of cable 130 are tied together and connected to a radio frequency source 232. The RF signal is conveniently a pulsed RF current with a peak amplitude of 1500 volts. The waveform is a sharply falling, damped, sinusoidal waveform, with a frequency of approximately 500 kHz. The pulse repetition rate is approximately 20 kHz. To complete the conduction from the RF source to ground, a grounded dispersive electrode 234 is placed in contact with the patient's skin. The surface area of contact should be as large as possible to avoid burns and shock effects. Consequently, the RF to ground passes from the tip 80 through the patient during endoscopic tissue cauterization.

Conveniently, the generator has the following operational controls: on/off foot switch for vibration; aspiration and light; continuous/intermittent ultrasonic vibration; vibration amplitude; optionally a switch 230 for connecting the EUA to an RF source.

Referring to Figure 14, the operating end of the open channel endoscopic ultrasonic aspirator, generally designated 310, includes a telescope 312 and a resonator 314.

The telescope 312 is mounted within a hermetically sealed tube or upper cavity 316. The telescope 312 includes a cylindrical lens system (not shown) and at least one optical fiber (not shown) that transmits light from a light source to the surgical field at the end of the telescope. Other illumination sources may be employed. The cylindrical lens system allows the surgeon to view the surgical field through an eyepiece from a distance from the surgical field.

The resonator 314 is located within another hermetically sealed tube or lower cavity 318. The resonator 314 is a tube cut open from its working end at least to the node 332 of the aspirator 310. The significance of the node 332 is discussed in detail below. Alternatively, the resonator 314 can be cut open along its entire length. As a result, the cut open portion of the resonator 314 takes the form of a channel having a U-shape in cross section.

If the resonator 314 and the lower cavity 318 are cut open along their entire length, the telescope 312 is partially suspended within this opening and an aspirator of the smallest size is obtained along the entire length. The housing 320, made of solid material, serves primarily to hold the telescope 312 in position above the cut open portion of the resonator 314 and the cavity 318.

Opening the operating tip of resonator 314 has no effect on its ultrasonic performance, provided that at least half of the tip is retained. Dissection rates are unaffected because in normal use only the lower half of the tip contacts the tissue, and the tissue slices removed by ultrasonic dissection using complete tubular tips never reach the size of a full drill diameter.

In one embodiment, the resonator 314 is cut open only to the node 332. This makes the operating portion of the aspirator smaller than the opposite end containing the cavity 318. As shown in Figures 14 through 18, the tubular housing 20 surrounding the telescope 312 and the resonator 314 is not round, but oval in shape to maintain the circumference of the EUA at the preferred minimum size. The oval housing provides for the housing of operating tools within the smallest possible circumference.

The upper cavity 316, in which the telescope 312 is housed, fits into the opening at the end of the resonator 314. The lower cavity 318, like the resonator 314, is a tube cut open from the operative end at least to the node 332 of the aspirator 310. The lower cavity 318 is attached to the upper cavity 316 by two beads of adhesive sealant 326, e.g. epoxy, so that the upper cavity 316 fits into the opening of the lower cavity 318, as shown in detail in Fig. 16. The upper cavity 316 and the lower cavity 318 can be made of any semi-rigid material. However, if the upper and lower cavities 316 and 318 are made of an electrically insulated material, the upper and lower cavities 316 and 318 electrically isolate the resonator 314 from the rest of the aspirator 310, the patient, and the surgeon so that the resonator 314 can be safely exposed to electrocautery current.

In order to maintain the tip of the resonator 314 adjacent and very close to the upper cavity 316, the plug 322 is inserted into the lower cavity 318, between the lower surface of the resonator 314 and the upper, inner surface of the lower cavity 318. The plug 322 is crescent-shaped in cross-section so that its surfaces engage the lower surface of the resonator 314 and the upper, inner surface of the lower cavity 318, and the upper surface 316 penetrates into position within the opening of the U-shaped tip of the resonator 314, as can be seen in Figures 14 and 16. In addition to maintaining the position of the tip of the resonator 314 adjacent the upper cavity 316, the plug 322 is also beneficial in sealing the cavity of the aspirator 310, between the lower surface of the upper cavity 316 and the lower cavity 318, so that the aspiration channel 328, between the resonator 314 and the upper cavity 316, remains the only access to this cavity. As shown in Figures 22 and 23, another seal 546 is attached to the transformer input part and this completely prevents the removed material from coming into contact with the remaining parts of the aspirator.

Even without the plug 322 in position, fluids would enter the channel at the time of tissue setting. Since there is very little clearance between the resonator 314 and the upper cavity 316, flow is mainly confined to the end of the tip. The hydrodynamic resistance to flow under or outside the channel is greater than the resistance in the open channel; consequently, substantially all of the flow occurs in the intended manner, namely by suction through the lower cavity 318.

The plug 322 is preferably made of a material that yields when it comes into contact with the ultrasonically vibrating tip of the resonator 314. By way of illustration, the plug 322 is made of epoxy or polyester resin, a thermoplastic or elastomeric material. When these compliant materials are used, any mechanical interference between the plug 322 and the ultrasonically vibrating tip of the resonator 314 is minimized or eliminated by physical abrasion after the tip of the resonator 314 begins to vibrate. During surgery, tissue aspiration occurs in the same manner as if the tip were a closed tube. Furthermore, direct vision of the entire surgical surface is possible because the dissecting edge of the tip appears as a "U" to surgeons viewing this edge through the telescope 312. This desirable vision cannot be achieved when using a closed tube aspiration tip.

The use of electrocautery current can prove to be an advantageous adjunct to endoscopic ultrasound surgery. In electrocautery, a metal tip, metal loop, or other surgical probe is connected to a high-voltage, high-frequency power source driven by a spark-gap oscillator or generator that produces the same pulsating electrical current flow characteristic of such oscillators. When the probe contacts tissue, this current flows through the tissue from the point of contact to a large collecting electrode placed beneath the patient and in direct contact with his or her skin.

If the ultrasonic tip is effectively isolated from the telescope and the sheath, it is possible not only to concentrate the electro-cauterizing potential directly on the tip, but also - if an isolated transducer is used to vibrate the tip - to simultaneously apply both ultrasonic vibration and electro-cauterization in one endoscopic instrument for the purpose of simultaneous dissection and cauterization, thereby reducing the duration of the surgical procedure.

The upper cavity 316 and the lower cavity 318 are hermetically sealed within the semi-rigid tubular housing 320. Due to the shape of the upper and lower cavities 316 and 318 and the manner in which they are connected to one another, a pair of irrigation fluid channels 324 are formed when the upper and lower cavities 316 and 318 are mounted within the housing 320 as shown in Figs. 14 and 16.

As discussed above, the resonator 314 has a U-shaped cross-section at its operative end, but in a preferred embodiment, has a closed tubular shape at node 332. A cross-sectional drawing of the aspirator at the location of node 332 in Figure 17 illustrates this. At node 332, both the resonator 314 and the lower cavity 318 have a tubular shape, and the aspiration channel 328 is circular in cross-section. Since the resonator 314 does not vibrate at node 332, the resonator 314 can contact the inner surface of the lower cavity 318 without adversely affecting the vibration of the aspirator 314 at its operative end. However, since the resonator 314 vibrates throughout its entire length except at the node 332, the remainder of the resonator 314 between node 332 and the converter that causes the resonator 314 to vibrate should cover the inner surface of the lower cavity 318. Consequently, as illustrated in Figs. 15 and 18, a space 330 exists between lower cavity 318 and resonator 314 in the aspirator between node 332 and the transducer.

During operation, after the aspirator of the present invention has been partially inserted into the body of a patient so that the operating end of the aspirator is positioned proximate the tissue to be removed by the aspirator, the resonator 314 is vibrated at an ultrasonic frequency by means of a transducer. As the resonator 314 vibrates at the ultrasonic frequency, the vibration at the tip of the resonator 314 enables it to sever the tissue. In order to remove the severed tissue from the patient's body, fluid is pumped to the surgical field through the aspirator's irrigation fluid channels 324. The irrigation fluid is removed from the surgical field by suction applied to the aspiration channel 328 of the resonator 314.

Because the end of the resonator 314 near the operating end has a U-shape in cross section, the irrigation liquid can flow into the aspirator channel 324 along the entire cut-open portion of the resonator 314 within the lower cavity 318, whereby the suction force can be reduced at any point along the cut-open portion. However, since the end portion of the lower cavity 328 is sealed by the plug 322 and only the U-shaped opening of the aspirator channel is left, the suction force is maintained within the lower cavity 318, so that sufficient suction force is maintained at the U-shaped tip of the resonator 314.

Although the most preferred shape of the resonator is a semicircle or U-shape in cross-section, other Shapes may be used. For example, a V-shape or open rectangular or square shape with straight, angled or rounded corners is also acceptable. Providing any of these shapes for a channel means (e.g., a bottom portion with two sides and an open roof) is within the scope of this invention. Also, the plug 322 would be designed to match the configuration of the resonator tip.

If the optimum minimum size of the aspirator is desired, the cutaway resonator 314 and lower cavity 518 should extend the entire length of the aspirator. This embodiment of the invention is shown in Figs. 19-24. Since the telescope 312 would be mounted partially within the resonator 314 and lower cavity 318, an arrangement of the instrument would be provided that would be similar in cross-section to Fig. 16, but would extend the entire length of the aspirator. The resonator is secured to node 332 by gasket 340. This gasket, which can be formed of rubber or other resilient material, would also prevent fluid from seeping into the space between the resonator 314 and lower cavity 518.

Figures 19 to 21 show the arrangement of the telescope 312 and the resonator 514 in the area of the transformer input part 342. As is most clearly seen in Figure 20, a notch 544 is cut in the upper part of the transformer input part 342 to provide space for the telescope 312. The telescope 512 is inserted into the notch 344 as shown in Figure 21. This notch 344 in the transformer input part 542, together with the open channel shape of the resonator 514, allows the telescope 512 to be partially fitted therein so that the outer diameter or French size of the entire aspiration system is kept to the minimum size.

In this embodiment, the open channel resonator requires a mechanism at one point for connecting the open channel to a closed tube or passage for removing biological material and fluid from the aspirator into a waste container, receptacle or trap. The transformer input portion 342 shown in Figures 19 through 23 is bent at a predetermined angle to provide clearance for the telescope 312. The resonator channel 314 and the telescope 312 also split at this point. To prevent backflow of fluid and biological tissue into the telescope 312 or into the handpiece, a moldable elastomeric or thermoplastic material is required to seal this area.

Figures 23 and 24 show this sealing material 346 and the outer sheath 348 for this area of the aspirator. This sealing material 346, which is generally an elastic or thermoplastic, self-vulcanizing material of relatively low hardness or low degree of hardness (e.g. less than 80 Shore A), is essential in that the liquid to be removed through the lower cavity 318 does not contaminate or seep into the handpiece of the aspirator. During manufacture of the aspirator, after the telescope 312 has been placed in the resonator channel 314, the sheath 348 is placed around the hinge area and the synthetic, elastic or thermoplastic material is secured therebetween. Preferably, the molded material is made of synthetic rubber with a hardness of approximately 40 Shore A. Surprisingly, although high friction losses were to be expected in this arrangement, the actual losses are very low, since in the encapsulated area the actual frequencies and vibration velocities are very low. Consequently, the Isolating the handpiece of the system from the fluid removed from the patient's body without reducing the vibration force transmitted to the operating tip of the aspirator. The seal 346 also isolates the system from the atmosphere.

Referring to Figure 24, it can be seen that the seal 340 prevents the fluid to be removed from the patient from flowing under or outside the resonator 314, namely between the resonator 314 and the lower cavity 318. This seal 340, however, does not obviate the need for the molded sealing material 346, since the molded sealing material is used to prevent the fluid located in the lower cavity 318 from contaminating the handpiece of the entire aspiration system.

Referring to Figures 25-27, there are shown various additionally modified operative tip configurations and designs for the resonator 314 of the invention. As shown in Figure 27, the operative tip may consist of a partially blocked channel, which provides advantages in terms of precision cutting of biological material. This same effect may be achieved by narrowing the channel means by flattening the tip or by reducing the cross-sectional area of other designs, e.g., by gradually reducing the cross-sectional area or size of the channel means, or by otherwise shaping the open area of the operative tip to be of a smaller dimension than that of the resonator 314.

In other embodiments, as illustrated in Figs. 25 and 27, the tip may comprise a portion of the tubular member which is also of the same diameter as the operating point. The end of the tube may be reduced by an overhang 350 or by crimping the end of the tube to limit the outer diameter at the operating point. This tubular design provides an advantage in that blockage of the resonator tube 314 is prevented since any removed biological material must pass through the small bore of the open tip to reach the tube 314. Consequently, the removed material could not block or clog the tube 314 when suction is used to remove this removed biological material.

Claims (23)

1. Vibration apparatus for an endoscopic ultrasound aspirator, comprising: a vibration source (70) for high frequency vibration and having a first amplitude; a first speed transformer (72) having an input and an output end, the input end being coupled to the vibration source (70) for vibration thereby, and the output end vibrating in response to the vibrations received at a second amplitude which is greater than the first amplitude; and a second elongated speed transformer (78) having an input and an output end, said output end corresponding to the working end (80) of the apparatus, and the input end of the second speed transformer (78) being connected to the front end of the first transformer (72) for vibration thereby, and the output end vibrating in response to the vibrations received at a third amplitude which is greater than the second amplitude, the second transformer (78) being of unitary construction and thus having a substantially constant mechanical stress level throughout its entire length during the vibration process. 2. A vibration apparatus according to claim 1, wherein the second speed transformer (78) is integrally connected to the front end of the first speed transformer (72) and the latter has a relatively thick, arcuate input portion (74). 3. Vibration apparatus according to claims 1 or 2, which additionally comprises a handpiece (20), said Vibration source (70) is mounted in the handpiece (20) and the input part of said first transformer is relatively large in cross-section and the output part of said first transformer is relatively small in cross-section. 4. Vibration apparatus according to claims 1, 2 or 3, wherein the first (72) and second (78) transformers and the vibration source (70) are elongated and have longitudinal axes, and wherein at least a portion of the first transformer is bent so that the longitudinal axis of the second transformer is offset from the longitudinal axis of the vibration source by a selected offset angle. 5. Vibration apparatus according to claims 1, 2, 3 or 4, wherein the vibration source (70) and the two transformers (72, 78) vibrate in an elongated form, with alternating internal motion nodes and antinodes, the vibration source in the handpiece (20) being attached to a motion node of the vibration source by flexible means between the interior of the handpiece and the vibration source, and the first transformer in the handpiece being attached to a motion node of the first transformer by flexible means between the interior of the handpiece and the first transformer, the latter motion node being located near the connection point between the input and output parts of the first transformer. 6. A vibration apparatus according to claims 2, 3, 4 or 5, further comprising viewing means mounted in the handpiece (20) for viewing a working field adjacent the output end of the second transformer from the handpiece. 7. A vibratory apparatus according to claim 6, wherein said viewing means is elongate and extends from the handpiece (20) to the work field along a path that is close and parallel to said second transformer and to said output portion of said first transformer and through a groove (90) formed in said input portion of said first transformer. 8. Endoscopic ultrasonic aspirator comprising: the vibration apparatus of claim 1, wherein the vibration source (70) is retained within a hollow handpiece (20) for generating mechanical vibrations in response to alternating current supplied to said vibration source; an elongated sheath (22) having a hollow bore for access to the interior of the hollow handpiece (20) and having a working end (80) facing away from the handpiece (20); Means for supplying alternating current to said vibration source; said second speed transformer corresponding to an elongated tool means (78) and coupled to the vibration source through the first speed transformer and leading through the hollow bore of the shell to a working field behind the working end of the shell for imparting said mechanical vibrations to the working field; viewing means (28) leading from the handpiece to the work area and providing a view of said work area from the handpiece; means for supplying fluid into a fluid space located between said tool means and said hollow bore of said shell; and Liquid detection means (124) for detecting the presence of liquid in the liquid space, connected to the means for supplying alternating current for detecting the alternating current supplied, and consequently for shutting off the mechanical vibrations when the liquid is not present. 9. Apparatus according to claim 8, wherein the liquid indicating means (124) includes an electrical means coupled to the liquid compartment for sensing the electrical load capacity in the liquid compartment, as well as for shutting off the alternating current supplied when the load capacity has exceeded the predetermined level indicating the absence of liquid. 10. Apparatus according to claim 9, wherein said electrical means (124) includes a conductivity detector, and wherein said conductivity is measured between said detector (124) and said tool means (78). 11. Apparatus according to claim 10, wherein said finder (124) is mounted within the enclosure (22) and extends substantially parallel to the tool means. 12. Apparatus according to claim 10, wherein the viewing means (28) extends through a second bore in the enclosure which is not exposed to the liquid from said liquid space; and wherein the viewfinder (124) is mounted within the second bore. 13. Apparatus according to any one of claims 8 to 12, wherein said tool means and said working head means (80) each comprise open channel means and means for supporting said open channel means in the form of a resilient plug (82), and which means for locking the coupling between said open channel means and said vibration source. 14. Apparatus according to any one of claims 8 to 13, wherein said tool means comprises a cylindrical tubular means (78), and wherein said working head means (80) is smaller in bore diameter than said cylindrical tubular means by being tapered, crimped or dammed along its outer diameter to achieve a smaller bore. 15. Apparatus for removing unwanted biological material, comprising: a) a handpiece (20); b) an elongated sheath extending from the handpiece and having a hollow bore therethrough; c) the vibration apparatus of claims 1, 2, 3, 4, 5 or 6 mounted in the handpiece (20), wherein the first (72) and second (78) transformers are mounted in and spaced from the hollow bore within the sheath, and the second transformer is coupled to the first transformer for amplifying the vibrations to a sufficient speed to dissolve the unwanted tissue; d) said second transformer has a working head (80) extending over the end of the sheath (22) facing away from the handpiece (20); e) said vibration source (70) and said two transformers (72, 78) are elongated and have a hollow bore (110) extending therethrough along a common longitudinal axis thereof, and forming: (i) a first fluid passage (96) in a space (98) located between the transformers (72, 78) and the enclosure; and (ii) a second fluid passage (98) along said common longitudinal axis; f) means (92, 94) for introducing liquid into one of the said liquid passages for the purpose of flushing or sprinkling an operating field adjacent to the working head of the second transformer; and g) means (122) for applying suction to the other said fluid passageway to remove the fluid and dissolved unwanted tissue from the surgical field. 16. Apparatus according to claim 15, wherein said means for applying suction to said other fluid passageway comprises: tubing means (122) for receiving the fluid and tissue; biopsy valve means (172) coupled to said tubing means (122) for selectively draining fluid and tissue from said tubing means; Biopsy collection means (176) for collecting the fluid and tissue selectively drained from said tubing means for filtering the selected tissue; Pump means (210) for applying suction to said biopsy collection means (176) and to said tubing means. 17. Apparatus according to claim 16, additionally comprising a main collecting means (180) for receiving the liquid and the tissue, which are not selectively discharged from the tubing means, and wherein said working head (80) is blunt. 18. Apparatus according to claims 15 or 16, wherein said working head (80) additionally comprises an open channel means allowing viewing of said head during use of the aspirator. 19. Apparatus according to claims 15, 16 or 17, wherein the entire length of the hollow through bore (110) of said vibration source and said transformers in the form of an open channel means (at 314) is oriented and dimensioned to partially receive, hold and support said viewing means, thereby reducing the size of said aspirator. 20. Apparatus according to claims 18 or 19, wherein said open channel means has a U-shaped or V-shaped cross-sectional orientation. 21. Apparatus according to claims 15, 16 or 17, wherein said working head means (80) extends beyond the end of the sheath, remote from the handpiece (20), and said working head means is smaller in size than the output end of said second transformer (78). 22. Apparatus according to claim 20, wherein said second transformer (78) comprises a first cylindrical tubular means and said working head means (80) comprises a second cylindrical tubular means of a smaller diameter than said first tubular means. 23. Apparatus according to claim 20, wherein said second transformer (78) tapers and decreases in diameter to the dimensions of the smaller diameter of the second tubular means.